The invention relates to a method for planning a cellular radio network, comprising creation of a model representing the cellular radio network and its radio environment on a digital map.
Cellular radio network planning can be divided into coverage, frequency, capacity, parameter and transmission planning. Planning applications based on digital maps have recently been developed for coverage, frequency and capacity planning. Such planning applications enable the modelling of the radio environment of the cellular radio network as a function of location. One example of such planning applications is the Network Planning System NSP/X of Nokia. The operation of the software is based on a mathematical propagation model for calculating the coverages of base stations located on a digital map.
Another example of conventional network planning tools is disclosed in WO 90/10342, wherein radio channels radio are allocated to the cells by utilizing an exclusion matrix presenting the interactions among the cells in the system. The allocation of radio channels is iteratively changed until it is optimal from the point of view interference.
One sub-area of radio network planning, i.e., the definition of network parameters has conventionally been carried out manually, by applying the method of "trial and error". Such network parameters include hand-over parameters, subscriber station and base station power control parameters and frequency hopping parameters. Parameter planning starts by defining a so-called "intelligent guess" for proper parameter values, which are then applied, as such, to the base stations of a planned and established cellular network. Information is then collected on the operation of the real radio network and analysed, and required changes in the network parameters are made on the basis of the analysis, which usually means a new "intelligent guess". A problem with the operational analysis of radio networks is the acquisition of requisite feedback information. The most important sources of feedback information have usually been the statistics of the mobile switching centre and the feedback from the network users. Within the most critical areas of the network, it is also possible to perform actual field strength measurements, on the basis of which one attempts to define proper parameter values. However, this process is extremely slow and laborious, and the network performance to be obtained by it is only satisfactory.
Careful parameter planning thus always requires a good knowledge of the local radio environment of the real cellular network as well as reliable estimations of the effects of the different control parameters in the heterogeneous radio environment typical of cellular networks. Problems associated with the parameter planning have become more concrete with the introduction of dense micro-cell networks. In addition, the parameter planning will become even more important with the introduction of GSM mobile networks, which is due to the decreased cell size and the more diversified and more complicated control algorithms and control parameters. Therefore, the effect of control parameters on the performance of real cellular radio networks will be a matter of great importance.